1. Field of the Invention
This invention relates to drag-reducing components located in the vicinity of wing-mounted aircraft engines.
2. Prior Art
In the normal practice of aircraft design and development, various manufacturers and designers must combine their individual efforts to arrive at a final configuration of a production aircraft. No single corporation or entity has the responsibility of developing all of the individual components required to power and lift a jet airplane. The practice of combining efforts is particularly evident in structures associated with wing-mounted engines on commercial jet airplanes. Responsibilities are typically divided between an engine manufacturer, designing, and supplying the engine and sometimes the nacelle, and an airframe manufacturer that develops and supplies the pylon and wing.
Normally, each of these individual manufacturers independently develops the final details of the physical package for their respective aircraft component and then cooperates with the other manufacturer to develop interface components. This combination of efforts has, in the past, resulted in complete, integrated, properly operating jet aircraft.
Each manufacturer also analyzes aerodynamic effects, including resistance drag, of their individual components. Before the aircraft is assembled, an experimentally determined value of aerodynamic drag of each of the individual components is added together to arrive at a total estimated resistance drag of the entire assembled aircraft. Often, this summation value is a reasonable approximation of the actual drag of the assembled aircraft as measured in actual flight. But, suprisingly, in many actual aircraft the measured drag is significantly higher than the value calculated by summing the drag of the individual components. The result is that the total drag of the assembled airplane is often higher as a result of optimizing the drag characteristics of the individual components on an isolated basis, in comparison to what might be achieved by optimizing the drag characteristics of the fully assembled package.
Various theories have been offered for this higher than expected drag but, until recently, the cause has not been known. Extensive testing conducted in connection with the present invention has uncovered a flow phenomena occurring in the region of wing-mounted engines. Analysis of the test results has revealed that certain portions of the ambient airflow in the vicinity of wing-mounted engines are achieving supersonic velocities, shocking and separating, causing high aircraft drag. Further analysis by the inventor has revealed that the airflow reaches supersonic velocity because of a channeling effect on the airflow at the inboard sides of pylons suspending wing-mounted engines.